Clay Shirky criticizes the Semantic Web in his article, The Semantic Web, Syllogism, and Worldview, to which Sam Ruby accurately assesses, "Two parts brilliance, one part strawman."

Joe Gregorio responds to Shirky's piece with this very concrete statement:

This is exactly the point I made in The Well-Formed Web, that the value that the proponents of the Semantic Web were offering could be achieved just as well with just XML and HTTP, and we are doing it today with no use of RDF, no need to wait for ubiquitous RDF deployment, no need to wait for RDF parsing and querying tools.

Yet, in the "just XML" world there is no one that I know of working on a "layer" that lets applications access a variety of XML formats (schemas) and treat similar or even logically equivalent elements or structures as if they were the same. This means each XML application developer has to do all of the work of integrating each XML format (schema): N × M.

The difference between the RDF proponents and the XML proponents is fairly simple. In the XML-centric world parties can utilize whatever internal formats and data sources they want but exchange XML documents that conform to an agreed upon format, in cases where the agreed upon format conflicts with internal formats then technologies like XSLT come to the rescue. The RDF position is that it is too difficult to agree on interchange formats so instead of going down this route we should use A.I.-like technologies to map between formats. Note, that this doesn't mean transformations don't need to be done as Ken points out

The RDF model along with the logic and equivalency languages, like OWL (nee DAML+OIL),

Thus, if you are an XML practitioner RDF doesn't change much except new transformation techniques and technologies to learn.

Additionally as Clay Shirky points out, on investigation it isn't even clear whether the basic premises of  RDF and similar Semantic Web technologies is based on a firm foundation and sound logic. In conclusion Ken wrote,

One can take potshots at RDF for how it addresses the problem, and the Semantic Web for possibly reaching too far too quickly in making logical assertions based on relations modeled in RDF, but to dismiss it out of hand or resort to strawmen to attack it all while not recognizing the problem it addresses or offering an alternative solution simply tells me they don't see the problem, and therefore have no credibility in knocking RDF or the Semantic Web for trying to solve it.

I wonder if I'm the only one that sees the parallels between the above quote and statements that attributed to religious fundamentalists. I wonder if Ken is familiar with Perpetual Motion Machines? The problem they want to solve is real albeit impossible to solve. Does he also feel that no one has the credibility to knock any one of the numerous designs for one that have been proposed until the critic can themselves produce a perpetual motion machine?